Journal article
Gating Induces a Conformational Change in the Outer Vestibule of Enac
The Journal of general physiology, Vol.116(6), pp.781-790
12/01/2000
DOI: 10.1085/jgp.116.6.781
PMCID: PMC2231819
PMID: 11099347
Abstract
The epithelial Na+ channel (ENaC) is comprised of three homologous subunits (α, β, and γ). The channel forms the pathway for Na+ absorption in the kidney, and mutations cause disorders of Na+ homeostasis. However, little is known about the mechanisms that control the gating of ENaC. We investigated the gating mechanism by introducing bulky side chains at a position adjacent to the extracellular end of the second membrane spanning segment (549, 520, and 529 in α, β, and γENaC, respectively). Equivalent “DEG” mutations in related DEG/ENaC channels in Caenorhabditis elegans cause swelling neurodegeneration, presumably by increasing channel activity. We found that the Na+ current was increased by mutagenesis or chemical modification of this residue and adjacent residues in α, β, and γENaC. This resulted from a change in the gating of ENaC; modification of a cysteine at position 520 in βENaC increased the open state probability from 0.12 to 0.96. Accessibility to this side chain from the extracellular side was state-dependent; modification occurred only when the channel was in the open conformation. Single-channel conductance decreased when the side chain contained a positive, but not a negative charge. However, alterations in the side chain did not alter the selectivity of ENaC. This is consistent with a location for the DEG residue in the outer vestibule. The results suggest that channel gating involves a conformational change in the outer vestibule of ENaC. Disruption of this mechanism could be important clinically since one of the mutations that increased Na+ current (γN530K) was identified in a patient with renal disease.
Details
- Title: Subtitle
- Gating Induces a Conformational Change in the Outer Vestibule of Enac
- Creators
- Peter M Snyder - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242Daniel B Bucher - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242Diane R Olson - Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa 52242
- Resource Type
- Journal article
- Publication Details
- The Journal of general physiology, Vol.116(6), pp.781-790
- DOI
- 10.1085/jgp.116.6.781
- PMID
- 11099347
- PMCID
- PMC2231819
- NLM abbreviation
- J Gen Physiol
- ISSN
- 0022-1295
- eISSN
- 1540-7748
- Language
- English
- Date published
- 12/01/2000
- Academic Unit
- Molecular Physiology and Biophysics; Cardiovascular Medicine; Medicine Administration; Internal Medicine
- Record Identifier
- 9984025595902771
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